Flavonoids are refer generally to a series of compounds having two benzene rings containing phenolic hydroxyl groups, mutually connected with the central three-carbon atoms, having the structure shown as the general formula:

They are generally found in fruits, vegetables, tea, grape wine, seeds, or plant roots etc. Although they are not belonged as vitamins, they are demonstrated to have anti-oxidation functions and anti-inflammatory reaction effects, and also confirmed to have the effects of resisting or relieving the formation of tumors, relieving pain and relieving cardiovascular diseases or malaemia.
Flavonoids include flavones and flavonols. Flavones also include glycosylated flavones and non-glycosylated flavones.
U.S. Pat. No. 7,471,973 B2 issued on Oct. 29, 2002 disclose that flavonoids can be used in cosmetics but does not mention other effects. In addition, U.S. Pat. No. 6,451,837B1 issued on Sep. 17, 2002 discloses the neuroprotective effects of flavonoids.